Modification of the porphyrin chromophore by ring fusion: identifying trends due to annelation of the porphyrin nucleus

2001 ◽  
Vol 05 (03) ◽  
pp. 267-288 ◽  
Author(s):  
TIMOTHY D. LASH
Keyword(s):  
Soret Band ◽  
Spectral Shift ◽  
Aromatic Rings ◽  
Ring Fusion ◽  
Spectral Shifts ◽  
Hyper Spectral ◽  
Two Factors ◽  
Porphyrin Analogues ◽  
Soret Absorption ◽  
Soret Region

The effects exerted by fused aromatic rings on the UV-vis spectra of porphyrins are surveyed. Modified porphyrin chromophores with fused benzene, 1,2-naphthalene, 9,10-phenanthrene or phenanthroline rings are surprisingly little affected even when a maximum number of ring fusions are incorporated. Linearly annealed naphtho- or anthraporphyrins show large red shifts to the Q bands but the Soret absorptions are weakened and undergo only minor bathochromic shifts. Fluoranthoporphyrins give multiple bands in the Soret region, but the Q band region is virtually unaffected by this tetracyclic ring system. On the other hand, metal chelates of fluoranthoporphyrins show surprisingly strong bands near 600 nm. Benzothiadiazole rings split and weaken the Soret band, but the Q bands region is unexceptional. However, metal coordination again produces relatively intense bands near 600 nm. The most significant results were obtained for porphyrins with fused acenaphthylene rings. Monoacenaphthoporphyrins (41) have three Soret bands at 387, 431 and 454 nm, and the longest wavelength Q band is shifted to 658 nm. opp-Diacenaphthoporphyrin (43) further shifts these bands with two Soret absorbances at 443 and 470 nm, and an additional strong peak is observed at 692 nm. The metal complexes of these systems also show strong bands between 602 and 656 nm. Still larger effects are produced by tetraacenaphthoporphyrin (47), the dication for which in trifluoroacetic acid (TFA)–chloroform has a Soret absorption at 528 nm. Tetraaryltetraacenaphthoporphyrins (48) are even more red shifted, showing Soret bands between 556 and 570 nm for the free bases and 565 to 588 nm for the related dications. The lead(II) chelate for tetraphenylporphyrin (48a) shows an additional 'hyper' spectral shift that brings the Soret band to 604 nm, and this effect can also be achieved by introducing four meso-phenylethynyl substituents onto the tetraacenaphthoporphyrin nucleus (49). In addition, by combining these two factors for the lead(II) chelate of 49, a record-breaking value for the Soret band of 642 nm can be achieved. Spectral shifts due to ring annelation in porphyrin analogues are also discussed, including those for oxybenziporphyrins, oxypyriporphyrins, carbaporphyrins and sapphyrins.

scholarly journals Dissociation of catalase. A correlation between changes in sedimentation and spectroscopic properties accompanying dissociation of bacterial catalase in alkaline solution

1970 ◽  
Vol 118 (2) ◽  
pp. 319-323 ◽  
Author(s):  
Peter Jones ◽  
R. H. Pain ◽  
A. Suggett
Keyword(s):  
Sedimentation Coefficient ◽  
Spectroscopic Properties ◽  
Sedimentation Equilibrium ◽  
Prosthetic Group ◽  
Environmental Constraint ◽  
Degree Of Dissociation ◽  
Slow Moving ◽  
High Concentrations ◽  
Soret Absorption ◽  
Soret Region

1. At high concentrations, in 10mm-phosphate buffer, pH7.0, the sedimentation coefficient of bacterial catalase varies with concentration according to: [Formula: see text] with S020,w=11.30S and ks=6.29×10−3ml mg−1. Sedimentation-equilibrium experiments yield a molecular weight of 240000. 2. Parallel studies of changes in sedimentation-velocity behaviour and in electronic spectra of bacterial catalase at pH>11 were made. Dissociation is indicated by the appearance of a slow-moving (2.9S) component in sedimentation patterns and this is accompanied by marked changes in absorption spectrum in the Soret region. Values of R=E406/E355 show a theoretically predictable near-linear dependence on α, the degree of dissociation calculated from ultracentrifuge data. 3. The Soret absorption of bacterial catalase subunits is much lower than that of the native enzyme, and it is suggested that dissociation produces an environmental constraint on the prosthetic group that results in distortion of the porphyrin ring.

scholarly journals Interpretations of cosmological spectral shifts

Open Physics ◽  
2013 ◽  
Vol 11 (3) ◽  
Author(s):  
Dag Østvang
Keyword(s):  
Hyperbolic Space ◽  
Spectral Shift ◽  
Space Time ◽  
Flat Connection ◽  
Closed Space ◽  
Spectral Shifts

AbstractIt is shown that for Robertson-Walker models with flat or closed space sections, all of the cosmological spectral shift can be attributed to the non-flat connection (and thus indirectly to space-time curvature). For Robertson-Walker models with hyperbolic space sections, it is shown that cosmological spectral shifts uniquely split up into “kinematic” and “gravitational” parts provided that distances are small. For large distances no such unique split-up exists in general. A number of common, but incorrect assertions found in the literature regarding interpretations of cosmological spectral shifts, is pointed out.

scholarly journals Solvatochromic Study of Two Pyridazinium Ylids Binary Solutions

2016 ◽  
Vol 22 (3) ◽  
pp. 598-602
Author(s):  
Daniela Babuşca ◽  
Cezarina Ana Moroşanu ◽  
Dana Ortansa Dorohoi
Keyword(s):  
Solubility Parameter ◽  
Intramolecular Charge Transfer ◽  
Spectral Shift ◽  
Solvent Interactions ◽  
Binary Solutions ◽  
Spectral Shifts ◽  
Different Types ◽  
Linear Solvation Energy ◽  
Solvent Molecules ◽  
Parameter Values

Abstract The wavenumbers in the maximum of intramolecular charge transfer (ICT) visibile band of two pyridazinium ylids binary solutions were analized using Kamlet and Taft empirical parameters and the Hildebrand’s solubility parameter. The Hildebrand’s solubility parameter values, δH2, measures the energy needed to separate the solvent molecules. A linear solvation energy relationship (LSER) allows separating the contributions of different types of interactions to the total spectral shift. The supply of universal and specific interactions as well as the supply of solvent-solvent interactions to the total spectral shifts was calculated.

scholarly journals Graphical Optimization of Spectral Shift Reconstructions for Optical Backscatter Reflectometry

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6154
Author(s):  
Daniel C. Sweeney ◽  
Dennis M. Sweeney ◽  
Christian M. Petrie
Keyword(s):  
Adaptive Algorithm ◽  
Spanning Tree ◽  
Mechanical Strain ◽  
Adaptive Algorithms ◽  
Spectral Shift ◽  
Reference Measurement ◽  
Interferometric Technique ◽  
Quality Metric ◽  
Spectral Shifts ◽  
Maximum Spanning Tree

Optical backscatter reflectometry (OBR) is an interferometric technique that can be used to measure local changes in temperature and mechanical strain based on spectral analyses of backscattered light from a singlemode optical fiber. The technique uses Fourier analyses to resolve spectra resulting from reflections occurring over a discrete region along the fiber. These spectra are cross-correlated with reference spectra to calculate the relative spectral shifts between measurements. The maximum of the cross-correlated spectra—termed quality—is a metric that quantifies the degree of correlation between the two measurements. Recently, this quality metric was incorporated into an adaptive algorithm to (1) selectively vary the reference measurement until the quality exceeds a predefined threshold and (2) calculate incremental spectral shifts that can be summed to determine the spectral shift relative to the initial reference. Using a graphical (network) framework, this effort demonstrated the optimal reconstruction of distributed OBR measurements for all sensing locations using a maximum spanning tree (MST). By allowing the reference to vary as a function of both time and sensing location, the MST and other adaptive algorithms could resolve spectral shifts at some locations, even if others can no longer be resolved.

Electromagnetic radiation and inertial forces

2019 ◽  
Vol 32 (4) ◽  
pp. 480-483
Author(s):  
Nasko Elektronov ◽  
Zhivko Kushev
Keyword(s):  
Electromagnetic Radiation ◽  
Doppler Effect ◽  
Inertial Force ◽  
Spectral Shift ◽  
Inertial Forces ◽  
Spectral Shifts ◽  
Nearby Stars ◽  
The Doppler Effect

The influence of the Coriolis inertial force generated by the orbital and spin motions of distant objects on the electromagnetic radiation energies during the exchange of photons between such objects has been considered. A red or blue spectral shift occurrence in a passive observation mode that is not associated with the Doppler effect or other known effects has also been shown. The relations found are used to calculate the spectral shifts for several nearby stars from our galaxy, as well as the spectral shifts of several galaxies. The results are close to the values currently observed.

Feature selection for cross-scene hyperspectral image classification using cross-domain ReliefF

2019 ◽  
Vol 17 (05) ◽  
pp. 1950039 ◽  
Author(s):  
Minchao Ye ◽  
Yongqiu Xu ◽  
Chenxi Ji ◽  
Hong Chen ◽  
Huijuan Lu ◽  
...  
Keyword(s):  
Feature Selection ◽  
Hyperspectral Image ◽  
Classification Problem ◽  
Spectral Shift ◽  
Simple Problem ◽  
Spectral Bands ◽  
Cross Domain ◽  
Two Factors ◽  
Single Dataset ◽  
Selection Algorithms

Hyperspectral images (HSIs) have hundreds of narrow and adjacent spectral bands, which will result in feature redundancy, decreasing the classification accuracy. Feature (band) selection helps to remove the noisy or redundant features. Most traditional feature selection algorithms can be only performed on a single HSI scene. However, appearance of massive HSIs has placed a need for joint feature selection across different HSI scenes. Cross-scene feature selection is not a simple problem, since spectral shift exists between different HSI scenes, even though the scenes are captured by the same sensor. The spectral shift makes traditional single-dataset-based feature selection algorithms no longer applicable. To solve this problem, we extend the traditional ReliefF to a cross-domain version, namely, cross-domain ReliefF (CDRF). The proposed method can make full use of both source and target domains and increase the similarity of samples belonging to the same class in both domains. In the cross-scene classification problem, it is necessary to consider the class-separability of spectral features and the consistency of features between different scenes. The CDRF takes into account these two factors using a cross-domain updating rule of the feature weights. Experimental results on two cross-scene HSI datasets show the superiority of the proposed CDRF in cross-scene feature selection problems.

scholarly journals The lobster carapace carotenoprotein, α-crustacyanin. A possible role for tryptophan in the bathochromic spectral shift of protein-bound astaxanthin

1991 ◽  
Vol 274 (1) ◽  
pp. 79-83 ◽  
Author(s):  
P F Zagalsky ◽  
E E Eliopoulos ◽  
J B C Findlay
Keyword(s):  
Vitamin A ◽  
Binding Sites ◽  
Untreated Control ◽  
Spectral Shift ◽  
Spectral Shifts ◽  
Tryptophan Residues ◽  
Tryptophan Modification ◽  
The Cross

Crustacyanin, cross-linked with dimethyl pimelimidate to stabilize the protein against denaturation, was used to test the effects of tryptophan modification with BNPS-skatole [3-bromo-3-methyl-2-(nitrophenylmercaptol)-3H-indole] on the ability of the apoprotein to recombine with astaxanthin. The cross-linked apoprotein re-forms alpha-crustacyanin with astaxanthin in reasonable yield following incubation of the protein under the conditions for tryptophan modification in the absence of BNPS-skatole. The BNPS-skatole-treated protein reconstitutes with astaxanthin to give a carotenoprotein with lambda max. at 472 nm, that of the carotenoid in hexane, in a yield similar to that of the BNPS-skatole-untreated control. The implied involvement of tryptophan residues at the sites of astaxanthin attachment in crustacyanin and their possible roles in the binding sites of vitamin A in vitamin A-proteins are discussed in relation to the bathochromic spectral shifts of the chromophores.

scholarly journals Accurate Prediction of Absorption Spectral Shifts of Proteorhodopsin Using a Fragment-Based Quantum Mechanical Method

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4486
Author(s):  
Chenfei Shen ◽  
Xinsheng Jin ◽  
William J. Glover ◽  
Xiao He
Keyword(s):  
Electric Fields ◽  
Electrostatic Interactions ◽  
Spectral Shift ◽  
Mechanical Method ◽  
Excitation Energies ◽  
Color Tuning ◽  
Spectral Shifts ◽  
Quantum Mechanical Method ◽  
Experimental Values ◽  
Molecular Fractionation

Many experiments have been carried out to display different colors of Proteorhodopsin (PR) and its mutants, but the mechanism of color tuning of PR was not fully elucidated. In this study, we applied the Electrostatically Embedded Generalized Molecular Fractionation with Conjugate Caps (EE-GMFCC) method to the prediction of excitation energies of PRs. Excitation energies of 10 variants of Blue Proteorhodopsin (BPR-PR105Q) in residue 105GLN were calculated with the EE-GMFCC method at the TD-B3LYP/6-31G* level. The calculated results show good correlation with the experimental values of absorption wavelengths, although the experimental wavelength range among these systems is less than 50 nm. The ensemble-averaged electric fields along the polyene chain of retinal correlated well with EE-GMFCC calculated excitation energies for these 10 PRs, suggesting that electrostatic interactions from nearby residues are responsible for the color tuning. We also utilized the GMFCC method to decompose the excitation energy contribution per residue surrounding the chromophore. Our results show that residues ASP97 and ASP227 have the largest contribution to the absorption spectral shift of PR among the nearby residues of retinal. This work demonstrates that the EE-GMFCC method can be applied to accurately predict the absorption spectral shifts for biomacromolecules.

scholarly journals Mechanism of peroxynitrite interaction with cytochrome c.

2003 ◽  
Vol 50 (3) ◽  
pp. 815-823 ◽  
Author(s):  
Lidia Gebicka ◽  
Joanna Didik
Keyword(s):  
Amino Acids ◽  
Protein Structure ◽  
Cytochrome C ◽  
Soret Band ◽  
Heme Iron ◽  
Tyrosine Nitration ◽  
Intermediate Products ◽  
Absorbance Changes ◽  
Kinetics Of ◽  
Soret Region

Kinetics of the reaction of peroxynitrite with ferric cytochrome c in the absence and presence of bicarbonate was studied. It was found that the heme iron in ferric cytochrome c does not react directly with peroxynitrite. The rates of the absorbance changes in the Soret region of cytochrome c spectrum caused by peroxynitrite or peroxynitrite/bicarbonate were the same as the rate of spontaneous isomerization of peroxynitrite or as the rate of the reaction of peroxynitrite with bicarbonate, respectively. This means that intermediate products of peroxynitrite decomposition, (.)OH/(.)NO(2) or, in the presence of bicarbonate, CO(3)(-)(.)/(.)NO(2), are the species responsible for the absorbance changes in the Soret band of cytochrome c. Modifications of the heme center of cytochrome c by radiolytically produced radicals, (.)OH, (.)NO(2) or CO(3)(-)(.), were also studied. The absorbance changes in the Soret band caused by radiolytically produced (.)OH or CO(3)(-)(.) were much more significant that those observed after peroxynitrite treatment, compared under similar concentrations of radicals. (.)NO(2) produced radiolytically did not interact with the heme center of cytochrome c. Cytochrome c exhibited an increased peroxidase-like activity after reaction with peroxynitrite as well as with radiolytically produced (.)OH, (.)NO(2) or CO(3)(-)(.) radicals. This means that modification of protein structure: oxidation of amino acids and/or tyrosine nitration, facilitates reaction of H(2)O(2) with the heme iron of cytochrome c, followed by reaction with the second substrate.

Sign in / Sign up

Export Citation Format

Share Document